Magnetron rapid frequency changer

[57] ABSTRACT

A magnetron is rapidly tuned over a wide bandwidth by inserting and withdrawing a conductive tuning element in an anode cavity. The conductive element is mounted on a plate which is moved in increments by a plurality of solenoids. A stop is mounted on the solenoids and each solenoid when actuated pulls the plate an incremental distance. The plate, when actuated by a single solenoid slides along the other solenoid rods in the solenoid array. A spring pushes the plate against the force of the solenoids and returns the plate to position of maximum element insertion, when the solenoids are de-energized.

Claims, 3 Drawing Figures

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PATENTED JUN 20 1972

SHEET 1 OF 2

3,671,801

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ATTORNEY

PATENTED JUN 2 ο 1972

3,671,801

SHEET 2 OF 2

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ATTORNEY

3,671,801

MAGNETRON RAPID FREQUENCY CHANGER

This invention relates to magnetrons and more particularly to a magnetron structure having electrically actuated parts for tuning the magnetron rapidly over a wide range of frequencies.

In some applications of magnetrons, it is required to rapidly tune the magnetron over a wide frequency band. In the past, tuning of the magnetron has been accomplished in a variety of ways. For example, the “pulling effect” is all often employed to tune a magnetron over a fraction of a percent bandwidth by mismatching the load coupled to the output of a magnetron. The “pushing effect” is also employed by varying anode voltage, although generally this effect is undesirable and is eliminated whenever possible even through tuning over a somewhat wider bandwidth (about 1 percent) can be obtained.

Recently, conductive tuning elements have been employed in magnetrons, which are movable in and out of the anode cavity spaces, to accomplish tuning. A cylindrical element is usually employed which has the same general conformation as ²θ the cavity but is somewhat smaller so that it may fit within the cavity without touching the sides. The magnetron tube is sometimes equipped with a diaphragm arrangement which can be flexed externally to thereby move the plunges in and out of the cavities, tuning the magnetron over a relatively wide ²⁵frequency band. For example, in some structures of this type, 50 percent bandwidth tuning has been accomplished. However, such plunger tuned magnetrons have not been readily tuned at high rates but are usually adjusted manually by an operator to produce a given frequency and once this frequency is established it is not changed again for sometime.

SUMMARY OF THE INVENTION

In accordance with the present invention a tunable element 35 is positioned within a cavity of a magnetron anode. The tuning element is attached to a plate, the plate being mounted on a number of solenoid rods. The solenoid rods are each of a unique length and each rod has a stop on its end. All rods are of a finite length and each rod is moved by its respective sole- 40 noid, a finite distance.

At the position of maximum tuning element insertion, the plate is held against one of the solenoid stops by a spring. As the first solenoid is actuated, the force of the solenoid applied to the stop lifts the plate and the element away from the mag- 45 netron anode, the plate sliding along the other solenoid rods inserted through the plate. When it is desired to remove the tuning element, an additional increment from the anode cavity, a second solenoid is operated applying a force to the plate through its respective stop element and sliding the plate along 50 the inactivated solenoids.

Accordingly, it is one object of this invention to provide a magnetron with a capability for rapid tuning over a wide frequency band.

Other features and object of the invention will be more apparent from the following specific description taken in conjunction with the drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a conventional solenoid anode block in top view and with a coupling in one of the resonant cavities.

FIG. 2 shows in perspective a portion of the anode block of FIG. 1 with a conductive element inserted within the resident cavity and fitted on a movable plate.

FIG. 3 shows in side view of an invention, shown in FIG. 2, taken along view line 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, the anode block 10, within a magnetron is shown as having cavity resonators 11, one of the cavity resonators designated 11', having a coupling loop 13 inserted therein for extracting RF energy.

The block structure shown in FIG. 1, shown in section in FIG. 2, with the cylindrically shaped tuning rod 15 inserted therein. Tuning rod 15 is mounted on plate 17. Plate 17 is shown as having a plurality of holes 19,21 and 23, and in each hole a solenoid rod 25, 27 and 29, respectively, is slidely fitted. At the end of each solenoid rod is a fixed stop, stop 31 $ on rod 25, stop 33 on rod 27, and stop 35 on rod 29. A solenoid coil is mounted on each solenoid rod, coil 43 on rod 25, coil 39 on rod 27 and coil 41 on rod 29.

A spring means 38, has a force in the direction of arrow 37 on surface 39 of plate 17, forcing plate 17 down against stop 33 of solenoid rod 27.

Referring now to FIG. 3, a side view along sections 3—3 of FIG. 2, is shown and wherein like numerals designate like and similarly operating parts. In FIG. 3, cavity resonator 11' is 15 shown partly in phantom. Conductive tuning element 15 is extended down in the cavity 11' and can be partially seen through slot 14 in block 10, the hidden portion of tuning element 15 within cavity resonator 11' being shown in phantom. The tuning element as shown in FIG. 2 and FIG. 3, is at its position of maximum insertion into cavity 11' and under spring force 37 is held in this position by stop 33 on rod 27.

OPERATION OF THE DEVICE

Operation of the device will now be described with reference to the solenoid actuators solenoid 39 on rod 27, solenoids 41 on rod 29 and solenoid 43 on rod 25. Actuation of these solenoids causes its respective rod to move in the direction as shown by arrow 45 in FIG. 3. Under spring force 37 the plate 17 is held against stop 33 on rod 27 and the tuning element is at its maximum insertion in cavity 11'.

To change the frequency of this device a first increment solenoid 43 is energized displacing solenoid rod 25 in the upward and vertical direction 45 and forcing stop 31 on rod 25 against plate 17. The continued upward movement of rod 25 to its point of maximum vertical displacement forces stop 31 to lift the plate 17 through a distance A and holds the plate at line 47.

As can be seen and is well known in the art, the retraction of tuning element 15 of cavity 11' for the distance A changes the frequency of the magnetron. In moving from its fully inserted position shown in FIG. 3, upward to level 47, the plate 17 slides along rod 27 and rod 29.

To change the frequency of the magnetron a second increment, solenoid 41 is actuated displacing rod 29 in a vertically upward direction 45, and bringing stop 35 against plate 17. As rod 25 continues its upward travel to its point of maximum vertical displacement, it drives plate 17 a distance B, from level 47 to lever 49, sliding plate 17 along solenoid rods 25 and 27. At level 49 plate 17 has moved an increment B or a total incremental distance A + B, by the operation of solenoids 43 and 41.

To change the frequency of the magnetron a third increment, solenoid 39 is operated drawing solenoid rod 27 in the upward vertical direction 45 and forcing plate 17, by stop 31, through the distance C, between level 49 and 51. In this position, plat® 17 has traveled a total distance of A + B + C. As is well known to those skilled in the art, the frequency of the magnetron will be unique for each of the levels 47,49 and 51.

In a similar manner the frequency of the magnetron may be changed by de-energizing sequentially each of the solenoids 39,41 and 43. This may be done as follows: To drive plate 17 from level 51 to level 49, solenoid 39 would be de-energized 65 and plate 17 under spring force 37 would be forced down against stop 35 on solenoid rod 29, stop 35 being at level approximately at level 49. Similarly to change the magnetron frequency to that when the plate 17 is at level 47, solenoid 41 would be de-energized and spring force 37 would similarly 70 force plate 17 down against stop 31 of solenoid rod 25 to level 47. Finally, to bring the operating frequency of the magnetron back to its point where the tuning element 15 has its maximum insertion into cavity 11', solenoid 43 would be de-energized and spring force 37 would similarly force plate 17 down 75 against stop 33 of tuning element 27.

3,671,801

By operating solenoids 43, 41 and 39 in sequence, or by operating each of the solenoids individually, the frequency of the magnetron can be rapidly changed over wide band limits.

Although the preferred embodiment shows solenoid actuated rods, the invention is not limited by the specific type of 5 actuator used. Obviously many other various means of actuation could be used such as hydraulic, or pneumatic or any other actuator which permits a mechanical force to be rapidly applied to the rods 25,27 and 29.

Obviously many modifications and variations of the present 10 invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.